From 1976 to 1996 the Swedish government actually banned wall to wall carpeting because they believed it worsened cases of allergies and asthma. Allergy and asthma cases nearly doubled during those twenty years. What they found was that carpet actually filters and purifies indoor air pollutants. The problem is that when the filter (carpet) gets full you have to change (clean) it. When people have only tile and other hard flooring surfaces, the pollutants settle on the floor but get stirred back up into the air every time the air conditioning or heat comes on. The key is to make sure to hire someone with a truck-mounted hot water extraction system that vents the air outside the house while cleaning. While vacuuming helps, many pollutants are so fine they pass right through the vacuum’s filter and go right back into the air. Also, chemical dry cleaning does nothing to help air quality as it employs no extraction in the process